1. Field of the Invention
The present invention relates to a fixing device for a steering device capable of tilt adjustment and having a very simple cam structure.
2. Description of the Related Art
Among tilt telescopic steering devices in which the height of a steering wheel and the orientation of the axis can be changed as appropriate to the body build and driving attitude of the driver, steering devices provided with a tilt adjustment mechanism whose structure includes an operation lever fitted to a lock bolt that passes through side plates of a fixed bracket installed on the car body and side plates of a movable bracket in which the steering column is installed, and by rotating the operation lever the side plates of the fixed bracket and movable bracket press against each other to lock the tilt are known.
Among this type of device are devices that include two cam members: one cam member fitted to the fixed bracket side, and the other cam member fitted to the operation lever for tilt adjustment, such as Japanese Patent Application Laid-open No. 2002-59851. This has a structure in which as a result of rotation of the operation lever, the cam surface of one cam member acts on the cam follower surface of the other cam member, so that the other cam member presses against the side part of the fixed bracket and the fixed bracket fixes the movable bracket. The cam member fitted to the operation lever is screwed to the threaded part of the tilt bolt. When the operation lever is rotated one cam member rotates, and acts on the cam follower surface of the other cam member fixed to the fixed bracket side part, so that the movable bracket side part presses against the fixed bracket side part.
This conventional cam configuration is shown in more detail in FIGS. 13A through 13C. The configuration includes a main drive cam 50 having a cam follower surface 51 (plateau 51a, slanting part 51b, valley 51c) and a driven cam 60 having a plurality of projections 61 that move up and down along the cam follower surface 51. The main drive cam 50 and driven cam 60 are fitted together. When the main drive cam 50 rotates relative to the driven cam 60, the locked state is when the projections 61 of the driven cam 60 rise onto the plateau 51a of the cam follower surface 51 of the main drive cam 50, and the released state is when the projections 61 of the driven cam 60 move from the plateau 51a of the cam follower surface 51 to the valleys 51c. 